This invention relates to another improvement in a series of inventions developed by the present inventors relating to printed circuit antennas having their elements capacitively coupled to each other, and in particular, two antennas wherein the feed to the radiating elements is coupled capacitively, rather than directly. The first in this series of inventions, invented by one of the present inventors, resulted in U.S. Pat. No. 4,761,654. An improvement to the antenna disclosed in that patent is described and claimed in U.S. patent application Ser. No. 06/930,187, filed on Nov. 13, 1986, now U.S. Pat. No. 5,005,019. The contents of the foregoing patents are incorporated herein by reference.
The antenna described in the foregoing U.S. patent and patent application permitted either linear or circular polarization to be achieved with a single feedline to the radiating elements. The antennas disclosed included a single array of radiating elements, and a single array of feedlines. One of the improvements which the inventors developed was to provide a structure whereby two layers of feedlines, and two layers of radiating elements could be provided in a single antenna, enabling orthogonally polarized signals to be generated, without interference between the two arrays. U.S. patent application Ser. No. 07/165,332, now U.S. Pat. No. 4,929,959 discloses and claims such a structure. The contents of that patent also are incorporated herein by reference.
Having developed the dual-band orthogonally polarized antenna, various experiments have been conducted with different shapes of radiating elements, and antenna configurations. Commonly assigned application Ser. No. 07/192,100, now U.S. Pat. No. 4,926,189 is directed to such an array employing gridded antenna elements. The contents of that patent also are incorporated herein by reference.
The work on dual polarized printed antennas resulted in the provision of an array which could operate in two senses of polarization, a lower array of the antenna being able basically to "see through" the upper array. The improvement represented by the present invention is to extend that concept.